Home stoves have always been given a casing that recalls daily-life objects, for example with a shape inspired by a piece of furniture or a clock. Thus, several generations of stoves have followed one another with a lifetime of at least forty years each: the bell stove, the Franklin stove, the ceramics step stove, the Godin-type stove, the cabinet stove, the convection stove, the cast-iron stove, the chimney stove, etc. Currently, a new generation of stoves, namely steel stoves of contemporary style, is supplanting cast-iron stoves.
Furthermore, household heating apparatuses using solid, liquid or gas fuel currently available on the market have a shape that is generally cubic, cylindrical, trapezoidal, etc., whether they are stand-alone apparatuses or inserted into masonry or a wall. One way of giving the current stoves a contemporary design, recalling daily-life objects that are currently in style and “trendy”, such as flat-screen televisions, smart phones or electronic tablets, is to make them both shallow, or even very shallow, and visually accessible from different angles, or even panoramic (FIGS. 1A and 1B).
However, the dimensions of most commercially-available stoves are often within the following limits:    height: 35-120 cm;    width: 30-100 cm;    depth: 30-70 cm.
The aforementioned dimensions, as well as the other features of current stoves, generally give them either a heavy or a bulky look, with related excess costs in terms of material, energy and handling.
These apparatuses may be very heavy and their weight may typically vary between 40 and 250 kg, depending on power. When they are inserted, these apparatuses require imposing masonry.
The depth is a particularly important parameter, since it determines the space available to fasten the door or window, and the back of the stove, as well as the size of the combustion chamber.
For example, in the case of woodstoves, it is difficult to reduce the depth of the stove given the restriction on the space available for inserting the logs, since the latter tend to pile on top of one another at the bottom of the stove and suffocate the combustion when the depth is reduced.
In general, it is observed that combustion in a narrow space using the prior-art combustion systems is not satisfactory: the yield is very average and the window quickly becomes dirty.
Until the end of the 1970s, woodstoves were supplied with fresh air coming from the grate at the bottom of the chamber, resulting in a tendency to make the stove deeper in order to avoid dirtying the window. Another solution was to suppress the windows, or to reduce them or to equip the stove with windows decorated with cast iron in order to hide the fouling.
A first way of trying to solve this problem of dirtying was to introduce fresh air along the window to create an air curtain that prevents the deposition of combustion residues and conveys them toward the rear of the chamber. However, introducing cold air or air at ambient temperature into a combustion chamber brought to a temperature of between 300 and 600° C. disrupts the combustion, and the efficiency is hence not optimized and the polluting emissions remain high.
In order to solve this problem, all (except in the startup phase) or part of the primary air introduced was preheated by contact with the hot walls of the chamber in secondary, or even tertiary, ducts, which defines a second and third combustion area (for example, see the “Woodbox”® patent—EP 1 563 228 B1, 100% primary air preheated safe startup). The stoves then become very complex and very expensive to manufacture.
Since the combustion occurs on several levels, the smoke crossing the incoming air, opening the door to reload with fuel may cause the living space to become smoky. To avoid this, it is necessary to improve the combustion by eliminating parasitic air intakes, therefore by making the chamber as sealed as possible, for example with a triple-walled loading door, which is again very expensive.
It is also difficult to reduce the depth of the prior-art stoves without significantly decreasing the volume of the combustion chamber, since a dual preheating duct for the primary air is often provided in the back and side walls of the apparatus, to promote good combustion.
In order to avoid significant dirtying at the level of the window, it is also necessary to burn “noble” wood i.e., expensive wood varieties such as oak, beech, hornbeam or birch, for example.
Several manufacturers have tried to give their heating apparatuses a “narrow” look by adding a frame around the existing apparatus. The total depth of these apparatuses, however, remains unchanged.
Furthermore, heating apparatuses working off gas are also known in which the preheating of the primary air comprises a dual enclosure that is concentric to the discharge duct for the burnt gases, which allows to recover part of the heat that is lost through the evacuation of smoke to preheat the incoming primary air.
Document EP 1 985 928 A1 describes a panoramic multi-fueled heating apparatus, where the primary air taken from outside the chamber is preheated in a dual-enclosure duct that is concentric with the hot discharge duct for the burnt gases. A heat exchanger situated in the crown of the furnace is used both as a baffle to slow down the discharge of the burnt gases and as a deflector that contributes to distributing all of the preheated air along the window(s), in the upper part of the combustion chamber.